How to Install Exterior and Interior doors.

Whether you are installing an exterior entry door or replacing one of your interior doors, few weekend projects will do more to dramatically improve the looks of your home or give you a greater sense of accomplishment. A mastery of basic carpentry skills, the following step-by-step guide and the following basic hand tools are all you’ll need to complete most of the job:

  • Hammer
  • Pry bar
  • Tape measure
  • Level
  • Utility knife
  • Nail set
  • Saw
  • Miter saw (for trim)

Although there are many door options out there, the style and crisp detailing of a quality hardwood door are really unmatched. Before you select the door of your dreams, you’ll want to get some essential measurements first.

Door Size
If you are replacing an existing door, measure the width and height of the door and then round up to the nearest inch to get the size of the replacement door you’ll need. For example, if your door measures 35-7/8 in. wide by 79-3/4 in. tall, you’ll order a 36-in. by 80-in. door.

Jamb width
For pre-hung doors, getting the right jamb width will ensure your door fits in the opening with trim sitting flush to the wall. The jamb width is measured from the backside of the interior trim to the backside of the exterior trim.

Rough opening
The rough opening is the opening into which the door frame is fitted. To get this measurement, you will need to remove any existing trim work on at least one side of the door. If replacing an exterior door, we recommend removing the interior trim while leaving the exterior trim in-tact (it will help to have the trim on one side later in the process).

Remove the old door

After you have your measurements, you are ready to begin the process of installing your door. If you are replacing an existing door, you will need to remove the previous door first, along with its frame. To begin, remove the previous door from the sill and remove the frame from the wall using a handsaw. Start by pulling the pins from the hinges (a hammer and nail set are useful for tapping the pins from the bottom) and removing the door from the frame. It’s also a good idea to lay a drop-cloth down to protect the floor. The old door may be heavy, so you may want an extra hand to help with this step.

Next, pry loose the old trim from the door frame, starting on the interior side. Most trim is caulked in, so you’ll want to score the intersection between the molding and jamb with a utility knife to allow the trim a clean release. Also, it’s a good idea to use a wide putty knife against the interior wall wherever you are prying to prevent the pry bar from damaging the wall. Follow these same steps to remove the exterior trim.

Jambs are generally paired with a door and we recommend against trying to reuse an existing jamb as it will be extremely difficult to get the door to swing properly. Using a handsaw, your next step is to cut completely through the side jamb to make it easier to tear out the entire frame. With one jamb cut, simply pry the jambs loose and pull them out of the opening.

Now you should be ready to begin the process of actually installing your new door following these steps:


Step 1: Prep the sill of the new door

Once the prior door frame is removed, check the condition of the opening to see if anything needs to be addressed or repaired. If any wood is rotted it is essential that it be removed. This is especially important to consider if you are replacing an exterior door. Check the sizing of the new sill. If it is thinner than the previous door sill, you will need to use caulk and additional wood to build up the sill area.

When setting the height of the sill, consider the type of flooring involved. Your door should go as close to the floor as possible without being stuck on the carpeting or rugs when it swings. Once the sill is installed you can use additional shims to level it and then fasten it with deck screws for reinforcement.

It is especially important that exterior doors are sealed, as this will prevent moisture from building up in your home. Use flashing take to cover the rough sill area. You should put the tape around the sides of the opening and front edges.


Step 2: Set the door in the opening

This is the most important step for ensuring your door swings properly in the opening. Before putting the door in place, this is the best time to ensure the building paper is still intact around the frame edges. The building paper provides protection for the walls from outside elements and should be covered with No. 15 felt if there are any tears or rips. After checking on the building paper, you may want to dry-fit your door in the opening and make any necessary adjustments to the frame to ensure your new door will fit. Once you are confident of a good fit, go ahead and apply a bead of caulk along the sides and top of the door opening and at the sill (according to the manufacturer’s instructions), and then tip the door into the opening. Since your door may be heavy, you may want someone available to help with this step.

With the door in the opening, your goal should be to center the door in the opening and use shims between the jambs and the frame to ensure the jambs are plumb and straight and that the door is level. When you’re happy with the fit, use galvanized casing nails to tack through the jamb and shims and into the framing.

Start inserting shims on the hinge-side jamb where it’s a good idea to ensure there are shims behind each hinge. If the gap is extra large, you may want to start with a piece of plywood and then finish with pairs of shims. It is most critical that the hinge-side jamb remain plumb. Once the jambs are secure and you’ve ensured they are still plumb, it’s a good idea to replace the screw closest to the inside of the jamb in each hinge with one long enough to reach the framing to keep the door from sagging over time.

Next insert shims in the latch-side jamb, inserting near the top, at the middle and near the bottom of the jamb. With this side, you are trying to ensure a consistent gap between the door and the doorjamb. Once you are pleased with the gap, proceed to secure the jamb with your galvanized casing nails.

With the door in place, you’ll next want to trim the shims so they are flush with the edge of the jambs. The simplest way to do this is to score the shim with a utility knife and then break them off. You may have to trim off any excess pieces protruding from the gap to ensure trim will lay flat over the opening.

Step 3: Insulate, caulk and install the trim

The final step to installing a door is to insulate, put up the trim and finish caulk. This final step is especially important for exterior doors. To insulate, fill the space between the doorjamb with minimal expanding foam installation, which you can purchase at your standard home goods store. Once the foam is expanded, skim over it to smooth it out and loosely stuff any leftover space with bits of fiberglass installation. Then, put up the interior trim or re-install the previous trim and use caulk to reinforce it. You’ll want to place the caulk in small beads between the siding and trim. Make sure that there are no gaps present and that the door and trim are sturdy. If the door is especially large, it may require an additional trim board underneath the sill so to support its most outer edge.

Once the door is up, the trim is in place and the entire structure is properly insulated, you can start focusing on the appearance of the door and use whatever paint or stain you’d like to have it match your household.

Congratulations! You now know how to install doors!